Syntheses and Reactions of 5-Alkyl- and 5-Aryl-11b-Methyl-1,2,3,11b-Tetrahydro-Pyrido[3,2,1-jk]carbazoles Having a Strychnos Alkaloids Partial Structure

Arylhydrazines 1 react with 2-methylcyclohexanone 2 via Fischer indole synthesis to 4a-methyl-2,3,3,4a-tetrahydro-1H-carbazoles 3, which cyclize with 2-substituted malonates 5 to give 5-aryl- and 5-alkylsubstituted 4-hydroxy-11b-methyl-1,2,3,11b-tetrahydro-6H-pyrido[3,2,1-jk]carbazol-6-ones 6. Pyridocarbazoles 6 can be shown to give a series of reactions, such as electrophilic halogenation to 5-chloro-pyridocarbazole-4,6-dione 9, and nucleophilic halogenation to 4-chloro-pyridocarbazol-6-one 11. 4-Azido-5-phenylpyridocarbazol-6-one 13 cyclizes under thermolysis to the indolo derivative 14. This reaction was studied by differential scanning calorimetry (DSC).